Why do I have to log in to see certain pages?

Because many of the books in Google Books are still under copyright, we limit the amount of these books that you can see. In order to enforce these limits, we make some pages available only after you log in to a Google Account. If you don't already have a Google Account, you can create one now. The aim of Google Books is to help you discover books and learn where to buy or borrow them, not read them online from start to finish. It's like going to a bookstore and browsing - with a Google twist.